551
FXUS65 KBYZ 121831
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
1231 PM MDT TUE MAY 12 2026
KEY MESSAGES
- HOTTEST DAY YET OF 2026 ON WEDNESDAY, WITH TEMPS IN THE UPPER
80S TO MID 90S (NEAR DAILY RECORD HIGHS).
- ISOLATED HIGH-BASED THUNDERSTORMS WEDNESDAY AFTERNOON/EVENING
COULD PRODUCE STRONG/ERRATIC WIND GUSTS.
- PACIFIC COLD FRONTAL PASSAGE WILL BRING STRONG WEST WINDS
WEDNESDAY NIGHT THOUGH THURSDAY; 60+ MPH GUSTS LIKELY ALONG THE
US-191 CORRIDOR FROM BIG TIMBER TO JUDITH GAP.
- NOT AS HOT (BUT STILL WARMER THAN NORMAL) THURSDAY & FRIDAY.
- TRENDING COOLER WITH INCREASING CHANCES OF PRECIPITATION
(INCLUDING MOUNTAIN SNOW) THIS WEEKEND.
DISCUSSION
THROUGH NEXT TUESDAY...
VERY BUSY WEATHER THE NEXT COUPLE OF DAYS.
RIDGE IS CURRENTLY BUILDING FROM THE WEST BUT TEMPS TODAY ARE
MODERATED BY EASTERLY SURFACE WINDS. THE RIDGE AXIS WILL SHIFT
EASTWARD OVER THE NEXT 24 HOURS, AS A PACIFIC TROF MOVES INLAND,
AND THE RESULTANT DOWNSLOPE WARMING AND DEEPENED THERMAL LOW OVER
CENTRAL MT WILL PUSH TEMPS TO THE UPPER 80S TO MID 90S TOMORROW.
WEDNESDAY WILL PUSH RECORD HIGHS AND BE THE HOTTEST DAY YET OF
2026. BUT ASIDE FROM THE HEAT IT WILL ALSO BE DRY (12-19% RH) WITH
BREEZY/MIXED SOUTHERLY WINDS. GRASSES HAVE GREENED UP NICELY BUT
THE WEATHER WOULD BE PROBLEMATIC IF THERE WAS A FIRE...SO
SOMETHING TO KEEP IN MIND. BY MID AFTERNOON AS SOME MODEST HIGH-
BASED SBCAPE IS ACHIEVED, AND AS HEIGHTS BEGIN TO FALL, WE WILL
SEE WEAK CONVECTION DEVELOP IN THE WEST AND TRACK EASTWARD INTO
THE EVENING. THESE STORMS (AND ANY WEAK CONVECTION, T-STORM OR
NOT) HAS THE POTENTIAL TO PRODUCE LOCALLY STRONG/ERRATIC WIND
GUSTS, ESPECIALLY OVER THE WESTERN HALF OF OUR FORECAST AREA. THE
COLD FRONT ITSELF WILL LAG BY A FEW HOURS THE ONSET OF CONVECTION,
BUT THERE COULD BE A FRONTAL/CONVECTIVE WINDS COMBO DURING THE
EVENING AND THIS WILL ALSO BE SOMETHING TO WATCH.
BEHIND THE FRONT AS THE CONVECTION ENDS, LARGE SCALE SUBSIDENCE
AND STRONG SYNOPTICALLY-FORCED WEST WINDS WILL TAKE OVER. THIS IS
ALSO WHERE MODELS DIVERGE. THE GFS (AS IT TYPICALLY IS) SHOWS
60-70 KNOTS OF 700MB WIND WHILE THE EC IS TAMER (NEAR 50 KNOTS).
BUT EVEN WITH THE TAMER SOLUTION WE WILL SEE STRONG WINDS ACROSS
OUR W/NW AND ENSEMBLES ARE HIGHLY SUGGESTIVE OF 60 MPH WIND GUSTS,
PERHAPS UP TO 70 MPH ALONG THE WESTERN FOOTHILLS. EXPECT IMPACTS
TO TRAVEL (ESP. US-191 FROM BIG TIMBER TO JUDITH GAP) AND CANNOT
RULE OUT SOME DOWNED TREES/POWER LINES IF THE HIGHER END WINDS
MATERIALIZE. HAVE ISSUED A HIGH WIND WATCH IN THE MOST CONFIDENT
REGION (WESTERN FOOTHILLS TO AS FAR EAST AS MUSSELSHELL AND SW
YELLOWSTONE COUNTIES) FROM WEDNESDAY EVENING TO THURSDAY EVENING.
AGAIN, IF THE STRONGER MID LEVEL FLOW VERIFIES WE COULD BE LOOKING
AT MORE WIDESPREAD STRONG POST-FRONTAL WINDS THAN THIS.
THURSDAY & FRIDAY ARE LOOKING DRY UNDER ZONAL FLOW, WITH BREEZY
WEST WINDS LINGERING FRIDAY. DESPITE THE "COOLER" TEMPS IT WILL BE
QUITE DRY WITH AFTERNOON RHS EXPECTED TO BE IN THE TEENS EACH OF
THESE DAYS. THE STRONG WINDS ON THURSDAY MAKE THIS THE MORE
PROBLEMATIC DAY OF THE TWO, REGARDING FIRE WEATHER.
A DEEPER PACIFIC TROF IS EXPECTED TO PUSH THRU THE NORTHERN
ROCKIES IN SOME FASHION THIS WEEKEND, BRINGING COOLER TEMPS AND
INCREASING PRECIPITATION CHANCES LATE SATURDAY THRU MONDAY. THIS
MAY BE A DYNAMIC ENOUGH SYSTEM TO PRODUCE ACCUMULATING SNOWFALL
OVER THE MOUNTAINS (HIGH CONFIDENCE EXISTS FOR MOUNTAIN PTYPE, IN
FACT), AND IF A PERIOD OF UPSLOPING MATERIALIZES WE COULD BE
LOOKING AT A DECENT PRECIP EVENT FOR OUR FOOTHILLS AND NORTH
ASPECTS. FURTHERMORE, THE PROBABILITY FOR WET SNOW ALONG THE
FOOTHILLS IS NON-ZERO. RED LODGE HAS A 35% CHANCE OF SEEING 1+
INCHES OF SNOW DURING THIS TIME. A PRECIPITATION TOTAL OF
0.15-0.65" IS A GOOD CURRENT ESTIMATE. LOOK FOR HIGH TEMPS TO FALL
TO THE 50S TO LOWER 60S FOR SUNDAY/MONDAY. AT THIS POINT, THE
HEAT AND WIND IMPACTS OVER THE NEXT TWO DAYS ARE THE MAIN
CONCERNS, BUT THE WEEKEND INTO EARLY NEXT WEEK IS LOOKING MORE
INTERESTING AND MODEL TRENDS NEED TO BE MONITORED. ANOTHER PACIFIC
WAVE MAY MOVE INTO THE REGION DURING THE MIDDLE OF NEXT WEEK, AS
CONSENSUS IS REASONABLY HIGH FOR A MORE ACTIVE WX PATTERN NEXT
WEEK.
JKL
AVIATION
18Z DISCUSSION...
WINDS MAY PICK UP WITH GUSTS OUT OF THE SE AT 20 KTS TOWARDS THE
VERY END OF THE PERIOD. VFR WIL PREVAIL, AND NO OTHER SIGNIFICANT
WEATHER IS FORECAST. WMR
PRELIMINARY POINT TEMP/POPS
WED THU FRI SAT SUN MON TUE
-----------------------------------------------------------
BIL 049/093 054/075 048/076 046/072 042/058 038/063 040/072
02/N 20/N 00/N 02/W 44/T 22/W 11/B
LVM 046/090 045/071 042/071 039/064 033/051 030/058 034/067
02/T 40/N 00/N 02/W 64/T 32/W 12/T
HDN 047/093 053/076 045/076 043/074 041/059 036/063 038/072
02/U 20/N 00/N 00/B 33/W 32/W 11/B
MLS 046/091 054/074 048/073 043/075 044/060 038/061 039/070
00/N 30/N 00/N 00/B 32/W 22/W 11/B
4BQ 046/091 054/074 045/073 043/075 044/058 037/059 038/069
00/U 20/N 00/U 00/B 33/W 32/W 21/B
BHK 041/085 052/073 044/071 041/074 042/059 035/058 036/068
00/N 20/N 00/N 00/B 43/W 32/W 12/W
SHR 042/092 047/075 039/072 039/074 036/054 032/058 033/068
02/U 20/N 00/U 00/U 36/T 54/W 12/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...HIGH WIND WATCH IN EFFECT FROM WEDNESDAY EVENING THROUGH
THURSDAY EVENING FOR ZONES 29-34-42-63-141-172-228-235.
WY...NONE.
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